<!DOCTYPE html>
<title>Tests CSS animation of anchor-size()</title>
<link rel="help" href="https://drafts.csswg.org/css-anchor-position-1/">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  #cb {
    border: 1px solid black;
    width: 400px;
    height: 400px;
    position: relative;
  }
  #anchor1, #anchor2 {
    width: 100px;
    height: 100px;
    background: tomato;
  }
  #anchor1 {
    background: coral;
    anchor-name: --a1;
  }
  #anchor2 {
    background: seagreen;
    anchor-name: --a2;
    width: 200px;
  }
  #anchored {
    width: 50px;
    height: 50px;
    background: skyblue;
    animation: --anim 9999s steps(2, start);
    position: absolute;
  }
  @keyframes --anim {
    from { width: anchor-size(--a1 width); }
    to { width: anchor-size(--a2 width); }
  }
</style>
<div id=cb>
  <div id=anchor1></div>
  <div id=anchor2></div>
  <div id=anchored></div>
</div>
<script>
  test(() => {
    assert_equals(anchored.offsetWidth, 150);
  }, 'Animation with anchor-size()');
</script>
